Sean, thanks for your comments.
One question I have here: Is timer service specific to EJB? I might not even
use EJBs and use something like Hibernate. Given this, I am wondering if
common application level services like Timer, are part of Servlets 2.3 or JSP
2.0
Also does anyone know when we could see the Final release of J2EE 1.4
reference implementation.
Thanks.
Pradeep
-----Original Message-----
From: Sean Brydon [mailto:Sean.Brydon@(protected)]
Sent: Wednesday, August 06, 2003 1:09 AM
To: J2EEPATTERNS-INTEREST@(protected)
Subject: Re: where to put the schedular
Hi,
regarding your question about J2EE 1.4
> Does anyone have more info on the Adaption of 1.4?!
You are correct that J2EE1.4 will have a J2EE timer service in the EJB
container and a Timer Bean which can receive notifications from the
timer service. I aggree that it will be a very nice standard feature for
J2EE.
J2EE1.4 is not FCS yet(specifications had to iron out some WSI support)
so is not finalized, so there are no complete 1.4 app servers available
yet, but they are coming soon. The J2EE 1.4 beta2 RI app server is
available now for download if you want to try a 1.4 app server at
http://java.sun.com/j2ee It has the J2EE 1.4 timer bean support as
well as web service support if you want to try some of the standard 1.4
features.
Below is a snippet from an Entity Bean used in the BluePrints Adventure
Builder new early access 3.1 release that shows usage of the timer
service. It will give you some idea of the usage.
import javax.ejb.*;
import
javax.ejb.Timer;
import java.util.*;
import com.sun.j2ee.blueprints.servicelocator.ejb.*;
public abstract class ManagerBean implements EntityBean, TimedObject {
private static final String TIMER_INTERVAL_ENV_NAME =
"java:comp/env/param/opc/OrderTrackingTimerInterval";
private EntityContext context = null;
// CMP fields
public abstract String getOrderId();
public abstract void setOrderId(String orderId);
public abstract String getStatus();
public abstract void setStatus(String status);
// EJB create methods
public String ejbCreate(String orderId, String status) throws
CreateException {
...set fields
}
public void ejbPostCreate(String orderId, String status) throws
CreateException {
try{
ServiceLocator sl = new ServiceLocator();
//get the timer interval in minutes and convert to milliseconds
long intervalDuration =
(Long.parseLong(sl.getString(TIMER_INTERVAL_ENV_NAME))) * 60000;
//timer starts after this duration in milliseconds
long initialDuration = 60000;
TimerService timerService = context.getTimerService();
Timer timer = timerService.createTimer(initialDuration,
intervalDuration, null);
}
catch(NumberFormatException ne){
throw new CreateException("Exception creating timer ! " +
ne.getMessage());
}
}
//method called by the contatiner when the timer goes off
public void ejbTimeout(Timer timer) {
updateOrderStatus();
}
//method to update order status
private void updateOrderStatus(){
String stat = getStatus();
if (stat.equalsIgnoreCase("PENDING")) {
setStatus("APPROVED");
}
if (stat.equalsIgnoreCase("APPROVED")) {
setStatus("SHIPPED_PART");
}
if (stat.equalsIgnoreCase("SHIPPED_PART")) {
setStatus("COMPLETED");
cancelTimer();
}
}
//method to cancel timers
private void cancelTimer(){
TimerService timerService = context.getTimerService();
Iterator iter = timerService.getTimers().iterator();
if(iter.hasNext()){
Timer timer = (Timer) iter.next();
timer.cancel();
}
}
hope that helps,
Sean
Stefan Frank wrote:
> Is this really such a good Idea?! The Timer starts a separate Thread for
> Scheduling - and this will interfere with the Thread-Pooling Mechanisms
> of most common App-Servers (Starting Threads in a Container was once
> considered a no-no in j2ee: If I remember it right, then there are
> mechanisms in the new JCA that allow you to request a thread from the
> AppServer.) Almost every vendor formerly had some proprietary extensions
> to perform at least basic Scheduling from inside the app-server - this
> has finally resulted in the introduction of a TimerService(
> http://www.theserverside.com/resources/article.jsp?l=MonsonHaefel-Column4)
> TimerService's can be created at runtime, so reading in a Table and
> setting up the Timers is possible. Using a TimerService should save you
> from being tied to the Database and also eliminates the need for a
> separate Box/process that runs outside your Appserver. But I'm not
> completely sure, which server already supports 1.4. Does anyone have
> more info on the Adaption of 1.4?!
>
> cheers
> stf
>
> Rangarajan , Suresh ( Cognizant ) wrote:
>
>> You can use the
java.util.Timer and TimerTask classes for this purpose.
>> On startup, you can read the tables and setup the timer.
>>
>> But, you can not dynamically change the values in the table...
>>
>>
>> -----Original Message-----
>> From: Pradeep Kumar [mailto:pradeepk@(protected)]
>> Sent: Tuesday, August 05, 2003 6:13 PM
>> To: J2EEPATTERNS-INTEREST@(protected)
>> Subject: where to put the schedular
>>
>>
>> Hello friends,
>>
>> This may not be the right forum to ask this question. But I couldn't
>> find the
>> appropriate forum.
>>
>> I have requirement, wherein I will have to run 2 types of schedulers.
>> I am
>> using DB2 8.1 and WebSphere 5 running on windows.
>>
>> One scheduler, should wake up on a particular date and time defined
>> in a
>> table and then updates some other tables.
>> Another scheduler, should wake up on a particular date and time
>> defined in a
>> table and then sends out emails.
>>
>> I think I have 3 options:
>> 1. Define and configure the schedulers using the DB2 tools.
>> 2. Build custom schedulers in my WebSphere application, that
>> periodically checks the system date with scheduled date and then
>> updates the
>> relevant table and also sends out email using the Java mail APIs
>> 3. write a stand alone java program and use a windows scheduler.
>>
>> These schedulers are purely back-end activities and do not depend on
>> the user
>> actions. The first option may be the appropriate one, but I am not
>> sure about
>> the implications.
>>
>> Your comments are appreciated.
>>
>> Thanks.
>> Pradeep Kumar
>> MindTree Consulting
>> 91 80 6711777 Xtn: 2033
>>
>>
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